Inter-rat (radio access technology) and intra-rat measurement reporting

ABSTRACT

A measurement report may trigger a handover based on relative signal strengths of a serving cell and an intra/inter-RAT (radio access technology) neighbor cell. This may result in a UE being handed over to a weak cell and cause a voice call to drop. A method of wireless communication includes determining whether to delay sending an inter-RAT or an intra-RAT measurement report based in part on a current status of a call setup and whether the UE and a network support an inter-RAT handover while in the current status of the call setup. The measurement report is delayed for a predetermined time period based in part on the determination. The method also includes sending the measurement report when the predetermined time period expire and/or the current status of the call setup changes to a new status when both the UE and the network support the inter-RAT handover.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 U.S.C. §119(e) to U.S.Provisional Patent Application No. 62/168,650, entitled “INTER-RAT(RADIO ACCESS TECHNOLOGY) AND INTRA-RAT MEASUREMENT REPORTING,” filed onMay 29, 2015, the disclosure of which is expressly incorporated byreference herein in its entirety.

BACKGROUND

Field

Aspects of the present disclosure relate generally to wirelesscommunication systems, and more particularly, to inter-radio accesstechnology (IRAT) and intra-RAT measurement reporting.

Background

Wireless communication systems are widely deployed to provide varioustelecommunication services, such as telephony, video, data, messaging,and broadcasts. Typical wireless communication systems may employmultiple-access technologies capable of supporting communication withmultiple users by sharing available system resources (e.g., bandwidth,transmit power). Examples of such multiple-access technologies includecode division multiple access (CDMA) systems, time division multipleaccess (TDMA) systems, frequency division multiple access (FDMA)systems, orthogonal frequency division multiple access (OFDMA) systems,single-carrier frequency divisional multiple access (SC-FDMA) systems,and time division synchronous code division multiple access (TD-SCDMA)systems.

These multiple access technologies have been adopted in varioustelecommunication standards to provide a common protocol that enablesdifferent wireless devices to communicate on a municipal, national,regional, and even global level. An example of a telecommunicationstandard is long term evolution (LTE). LTE is a set of enhancements tothe universal mobile telecommunications system (UMTS) mobile standardpromulgated by Third Generation Partnership Project (3GPP). It isdesigned to better support mobile broadband Internet access by improvingspectral efficiency, lower costs, improve services, make use of newspectrum, and better integrate with other open standards using OFDMA onthe downlink (DL), SC-FDMA on the uplink (UL), and multiple-inputmultiple-output (MIMO) antenna technology. However, as the demand formobile broadband access continues to increase, there exists a need forfurther improvements in LTE technology. Preferably, these improvementsshould be applicable to other multi-access technologies and thetelecommunication standards that employ these technologies.

SUMMARY

In an aspect of the present disclosure, a method of wirelesscommunication at a user equipment (UE) is presented. The method includesdetermining whether to delay sending an inter-RAT (inter-radio accesstechnology) measurement report or an intra-RAT measurement report basedat least in part on a current status of the call setup and whether boththe UE and a network support an inter-RAT handover while in the currentstatus of the call setup. The network may be a serving network or atarget network. The method further includes delaying sending theintra-RAT measurement report for an intra-RAT measurement report holdingtime period and/or the inter-RAT measurement report for an inter-RATmeasurement report holding time period based at least in part on thedetermination. The method also includes sending the intra-RATmeasurement report and/or the inter-RAT measurement report when theintra-RAT measurement report holding time period and/or the inter-RATmeasurement report holding time period expire and/or the current statusof the call setup changes to a new status in which both the UE and thenetwork support the inter-RAT handover.

In another aspect of the present disclosure, an apparatus for wirelesscommunication is presented. The apparatus includes means for determiningwhether to delay sending an inter-RAT (inter-radio access technology)measurement report or an intra-RAT measurement report based at least inpart on a current status of the call setup and whether both the UE and anetwork support an inter-RAT handover while in the current status of thecall setup. The network may be a serving network or a target network.The apparatus further includes means for delaying sending the intra-RATmeasurement report for an intra-RAT measurement report holding timeperiod and/or the inter-RAT measurement report for an inter-RATmeasurement report holding time period based at least in part on thedetermination. The method also includes means for sending the intra-RATmeasurement report and/or the inter-RAT measurement report when theintra-RAT measurement report holding time period and/or the inter-RATmeasurement report holding time period expire and/or the current statusof the call setup changes to a new current status of the call setup inwhich in which both the UE and the network support the inter-RAThandover.

In yet another aspect of the present disclosure, an apparatus forwireless communication is presented. The apparatus includes a memory, atleast one processor coupled to the memory and a transceiver configuredto communicated with a network. The processor(s) is configured todetermine whether to delay sending an inter-RAT (inter-radio accesstechnology) measurement report or an intra-RAT measurement report basedat least in part on a current status of the call setup and whether boththe UE and a network support an inter-RAT handover while in the currentstatus of the call setup. The network may be a serving network or atarget network. The processor(s) is further configured to delay sendingthe intra-RAT measurement report for an intra-RAT measurement reportholding time period and/or the inter-RAT measurement report for aninter-RAT measurement report holding time period based at least in parton the determination. The processor(s) is also configured to send theintra-RAT measurement report and/or the inter-RAT measurement reportwhen the intra-RAT measurement report holding time period and/or theinter-RAT measurement report holding time period expire and/or thecurrent status of the call setup changes to a new current status of thecall setup in which both the UE and the network support the inter-RAThandover.

In still another aspect of the present disclosure, a computer programproduct for wireless communication is presented. The computer programproduct includes a non-transitory computer-readable medium havingencoded thereon program code. The program code includes program code todetermine whether to delay sending an inter-RAT (inter-radio accesstechnology) measurement report or an intra-RAT measurement report basedat least in part on a current status of the call setup and whether boththe UE and a network support an inter-RAT handover while in the currentstatus of the call setup, the network being a serving network or atarget network. The program code further includes program code to delaysending the intra-RAT measurement report for an intra-RAT measurementreport holding time period and/or the inter-RAT measurement report foran inter-RAT measurement report holding time period based at least inpart on the determination. The program code also includes program codeto send the intra-RAT measurement report and/or the inter-RATmeasurement report when the intra-RAT measurement report holding timeperiod and/or the inter-RAT measurement report holding time periodexpire and/or the current status of the call setup changes to a newcurrent status of the call setup in which both the UE and the networksupport the inter-RAT handover.

In an aspect of the present disclosure, a method of wirelesscommunication at a network is presented. The method includes determiningwhether to delay sending to a user equipment (UE) an inter-radio accesstechnology (RAT) handover command or an intra-RAT handover command basedat least in part on a current status of a call setup and whether the UEand the network support an inter-RAT handover while in the currentstatus of the call setup, the network being a serving network or atarget network. The method further includes delaying sending theintra-RAT handover command for an intra-RAT handover holding time periodand/or the inter-RAT handover command for an inter-RAT handover holdingtime period based at least in part on the determination. The method alsoincludes sending the intra-RAT handover command and/or the inter-RAThandover command when the intra-RAT handover holding time period and/orthe inter-RAT handover holding time period expire, and/or the call setupchanges to a new current status in which both the UE and the networksupport the inter-RAT handover.

In another aspect of the present disclosure, an apparatus for wirelesscommunication is presented. The apparatus includes means for determiningwhether to delay sending to a user equipment (UE) an inter-radio accesstechnology (RAT) handover command or an intra-RAT handover command basedat least in part on a current status of a call setup and whether the UEand the network support an inter-RAT handover while in the currentstatus of the call setup, the network being a serving network or atarget network. The apparatus further includes means for delayingsending the intra-RAT handover command for an intra-RAT handover holdingtime period and/or the inter-RAT handover command for an inter-RAThandover holding time period based at least in part on thedetermination. The apparatus also includes means for sending theintra-RAT handover command and/or the inter-RAT handover command whenthe intra-RAT handover holding time period and/or the inter-RAT handoverholding time period expire, and/or the call setup changes to a newcurrent status in which both the UE and the network support theinter-RAT handover.

In yet another aspect of the present disclosure, an apparatus forwireless communication at a network is presented. The apparatus includesa memory and at least one processor coupled to the memory. Theprocessor(s) is configured to determine whether to delay sending to auser equipment (UE) an inter-radio access technology (RAT) handovercommand or an intra-RAT handover command based at least in part on acurrent status of a call setup and whether the UE and the networksupport an inter-RAT handover while in the current status of the callsetup, the network being a serving network or a target network. Theprocessor(s) is further configured to delay sending the intra-RAThandover command for an intra-RAT handover holding time period and/orthe inter-RAT handover command for an inter-RAT handover holding timeperiod based at least in part on the determination. The processor(s) isalso configured to send the intra-RAT handover command and/or theinter-RAT handover command when the intra-RAT handover holding timeperiod and/or the inter-RAT handover holding time period expire, and/orthe call setup changes to a new current status in which both the UE andthe network support the inter-RAT handover.

In still another aspect of the present disclosure, a computer programproduct for wireless communication at a network is presented. Thecomputer program product includes a non-transitory computer-readablemedium having encoded thereon program code. The program code includesprogram code to determine whether to delay sending to a user equipment(UE) an inter-radio access technology (RAT) handover command or anintra-RAT handover command based at least in part on a current status ofa call setup and whether the UE and the network support an inter-RAThandover while in the current status of the call setup, the networkbeing a serving network or a target network. The program code furtherincludes program code to delay sending the intra-RAT handover commandfor an intra-RAT handover holding time period and/or the inter-RAThandover command for an inter-RAT handover holding time period based atleast in part on the determination. The program code also includesprogram code to send the intra-RAT handover command and/or the inter-RAThandover command when the intra-RAT handover holding time period and/orthe inter-RAT handover holding time period expire, and/or the call setupchanges to a new current status in which both the UE and the networksupport the inter-RAT handover.

This has outlined, rather broadly, the features and technical advantagesof the present disclosure in order that the detailed description thatfollows may be better understood. Additional features and advantages ofthe disclosure will be described below. It should be appreciated bythose skilled in the art that this disclosure may be readily utilized asa basis for modifying or designing other structures for carrying out thesame purposes of the present disclosure. It should also be realized bythose skilled in the art that such equivalent constructions do notdepart from the teachings of the disclosure as set forth in the appendedclaims. The novel features, which are believed to be characteristic ofthe disclosure, both as to its organization and method of operation,together with further objects and advantages, will be better understoodfrom the following description when considered in connection with theaccompanying figures. It is to be expressly understood, however, thateach of the figures is provided for the purpose of illustration anddescription only and is not intended as a definition of the limits ofthe present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, nature, and advantages of the present disclosure willbecome more apparent from the detailed description set forth below whentaken in conjunction with the drawings in which like referencecharacters identify correspondingly throughout.

FIG. 1 is a block diagram conceptually illustrating an example of atelecommunications system.

FIG. 2 is a diagram illustrating an example of a downlink framestructure in LTE.

FIG. 3 is a diagram illustrating an example of an uplink frame structurein LTE.

FIG. 4 is a block diagram conceptually illustrating an example of a basestation in communication with a UE in a telecommunications system.

FIG. 5 illustrates exemplary network coverage areas including a firstRAT network and a second RAT wireless network according to aspects ofthe present disclosure.

FIG. 6 is a block diagram illustrating a wireless communication networkin accordance with aspects of the present disclosure.

FIG. 7 is an exemplary call flow diagram illustrating a signalingprocedure in accordance with aspects of the present disclosure.

FIG. 8 is a flow diagram illustrating an example decision process forintra-RAT and inter-RAT measurement reporting according to aspects ofthe present disclosure.

FIG. 9 is a flow diagram illustrating a method for intra-RAT andinter-RAT measurement reporting according to aspects of the presentdisclosure.

FIG. 10 is a flow diagram illustrating a method for intra-RAT andinter-RAT handover according to aspects of the present disclosure.

FIG. 11 is a block diagram illustrating differentmodules/means/components for inter-RAT and/or intra-RAT measurementreporting in an example apparatus according to one aspect of the presentdisclosure.

FIG. 12 is a block diagram illustrating differentmodules/means/components for inter-RAT and/or intra-RAT handover in anexample apparatus according to one aspect of the present disclosure.

DETAILED DESCRIPTION

The detailed description set forth below, in connection with theappended drawings, is intended as a description of variousconfigurations and is not intended to represent the only configurationsin which the concepts described herein may be practiced. The detaileddescription includes specific details for the purpose of providing athorough understanding of the various concepts. However, it will beapparent to those skilled in the art that these concepts may bepracticed without these specific details. In some instances, well-knownstructures and components are shown in block diagram form in order toavoid obscuring such concepts.

FIG. 1 is a diagram illustrating an LTE network architecture 100. TheLTE network architecture 100 may be referred to as an evolved packetsystem (EPS) 100. The EPS 100 may include one or more user equipment(UE) 102, an evolved UMTS terrestrial radio access network (E-UTRAN)104, an evolved packet core (EPC) 110, a home subscriber server (HSS)120, and an operator's IP services 122. The EPS can interconnect withother access networks, but for simplicity those entities/interfaces arenot shown. As shown, the EPS 100 provides packet-switched services,however, as those skilled in the art will readily appreciate, thevarious concepts presented throughout this disclosure may be extended tonetworks providing circuit-switched services.

The E-UTRAN 104 includes an evolved Node B (eNodeB) 106 and othereNodeBs 108. The eNodeB 106 provides user and control plane protocolterminations toward the UE 102. The eNodeB 106 may be connected to theother eNodeBs 108 via a backhaul (e.g., an X2 interface). The eNodeB 106may also be referred to as a base station, a base transceiver station, aradio base station, a radio transceiver, a transceiver function, a basicservice set (BSS), an extended service set (ESS), or some other suitableterminology. The eNodeB 106 provides an access point to the EPC 110 fora UE 102. Examples of UEs 102 include a cellular phone, a smart phone, asession initiation protocol (SIP) phone, a laptop, a personal digitalassistant (PDA), a satellite radio, a global positioning system, amultimedia device, a video device, a digital audio player (e.g., MP3player), a camera, a game console, or any other similar functioningdevice. The UE 102 may also be referred to by those skilled in the artas a mobile station, a subscriber station, a mobile unit, a subscriberunit, a wireless unit, a remote unit, a mobile device, a wirelessdevice, a wireless communications device, a remote device, a mobilesubscriber station, an access terminal, a mobile terminal, a wirelessterminal, a remote terminal, a handset, a user agent, a mobile client, aclient, or some other suitable terminology.

The eNodeB 106 is connected to the EPC 110 via, e.g., an S1 interface.The EPC 110 includes a mobility management entity (MME) 112, other MMEs114, a serving gateway 116, and a packet data network (PDN) gateway 118.The MME 112 is the control node that processes the signaling between theUE 102 and the EPC 110. Generally, the MME 112 provides bearer andconnection management. All user IP packets are transferred through theserving gateway 116, which itself is connected to the PDN gateway 118.The PDN gateway 118 provides UE IP address allocation as well as otherfunctions. The PDN gateway 118 is connected to the operator's IPservices 122. The operator's IP services 122 may include the Internet,the Intranet, an IP multimedia subsystem (IMS), and a packet switched(PS) streaming service (PSS).

FIG. 2 is a diagram 200 illustrating an example of a downlink framestructure in LTE. A frame (10 ms) may be divided into 10 equally sizedsubframes. Each subframe may include two consecutive time slots. Aresource grid may be used to represent two time slots, each time slotincluding a resource block. The resource grid is divided into multipleresource elements. In LTE, a resource block contains 12 consecutivesubcarriers in the frequency domain and, for a normal cyclic prefix ineach OFDM symbol, 7 consecutive OFDM symbols in the time domain, for atotal of 84 resource elements. For an extended cyclic prefix, a resourceblock contains 6 consecutive OFDM symbols in the time domain, resultingin 72 resource elements. Some of the resource elements, as indicated asR 202, 204, include downlink reference signals (DL-RS). The DL-RSinclude Cell-specific RS (CRS) (also sometimes called common RS) 202 andUE-specific RS (UE-RS) 204. UE-RS 204 are transmitted only on theresource blocks upon which the corresponding physical downlink sharedchannel (PDSCH) is mapped. The number of bits carried by each resourceelement depends on the modulation scheme. Thus, the more resource blocksthat a UE receives and the higher the modulation scheme, the higher thedata rate for the UE.

FIG. 3 is a diagram 300 illustrating an example of an uplink framestructure in LTE. The available resource blocks for the uplink may bepartitioned into a data section and a control section. The controlsection may be formed at the two edges of the system bandwidth and mayhave a configurable size. The resource blocks in the control section maybe assigned to UEs for transmission of control information. The datasection may include all resource blocks not included in the controlsection. The uplink frame structure results in the data sectionincluding contiguous subcarriers, which may allow a single UE to beassigned all of the contiguous subcarriers in the data section.

A UE may be assigned resource blocks 310 a, 310 b in the control sectionto transmit control information to an eNodeB. The UE may also beassigned resource blocks 320 a, 320 b in the data section to transmitdata to the eNodeB. The UE may transmit control information in aphysical uplink control channel (PUCCH) on the assigned resource blocksin the control section. The UE may transmit only data or both data andcontrol information in a physical uplink shared channel (PUSCH) on theassigned resource blocks in the data section. An uplink transmission mayspan both slots of a subframe and may hop across frequency.

A set of resource blocks may be used to perform initial system accessand achieve uplink synchronization in a physical random access channel(PRACH) 330. The PRACH 330 carries a random sequence. Each random accesspreamble occupies a bandwidth corresponding to six consecutive resourceblocks. The starting frequency is specified by the network. That is, thetransmission of the random access preamble is restricted to certain timeand frequency resources. There is no frequency hopping for the PRACH.The PRACH attempt is carried in a single subframe (1 ms) or in asequence of few contiguous subframes and a UE can make only a singlePRACH attempt per frame (10 ms).

FIG. 4 shows a block diagram of a design of a base station 410 and a UE450, which may be one of the base stations/eNodeBs and the UE in FIG. 1.For example, the base station 410 may be the macro eNodeB 106 in FIG. 1,and the UE 450 may be the UE 102 of FIG. 1. The base station 410 mayalso be a base station of some other type. The base station 410 may beequipped with antennas 434 a through 434 t, and the UE 450 may beequipped with antennas 452 a through 452 r.

At the base station 410, a transmit processor 420 may receive data froma data source 412 and control information from a controller/processor440. The control information may be for the physical broadcast channel(PBCH), physical control format indicator channel (PCFICH), physicalhybrid-ARQ indicator channel (PHICH), physical downlink control channel(PDCCH), etc. The data may be for the physical downlink shared channel(PDSCH), etc. The processor 420 may process (e.g., encode and symbolmap) the data and control information to obtain data symbols and controlsymbols, respectively. The processor 420 may also generate referencesymbols, e.g., for the primary synchronization signal (PSS), secondarysynchronization signal (SSS), and cell-specific reference signal. Atransmit (TX) multiple-input multiple-output (MIMO) processor 430 mayperform spatial processing (e.g., precoding) on the data symbols, thecontrol symbols, and/or the reference symbols, if applicable, and mayprovide output symbol streams to the modulators (MODs) 432 a through 432t. Each modulator 432 may process a respective output symbol stream(e.g., for OFDM, etc.) to obtain an output sample stream. Each modulator432 may further process (e.g., convert to analog, amplify, filter, andupconvert) the output sample stream to obtain a downlink signal.Downlink signals from modulators 432 a through 432 t may be transmittedvia the antennas 434 a through 434 t, respectively.

At the UE 450, the antennas 452 a through 452 r may receive the downlinksignals from the base station 410 and may provide received signals tothe demodulators (DEMODs) 454 a through 454 r, respectively. Eachdemodulator 454 may condition (e.g., filter, amplify, downconvert, anddigitize) a respective received signal to obtain input samples. Eachdemodulator 454 may further process the input samples (e.g., for OFDM,etc.) to obtain received symbols. A MIMO detector 456 may obtainreceived symbols from all the demodulators 454 a through 454 r, performMIMO detection on the received symbols if applicable, and providedetected symbols. A receive processor 458 may process (e.g., demodulate,deinterleave, and decode) the detected symbols, provide decoded data forthe UE 450 to a data sink 460, and provide decoded control informationto a controller/processor 480.

On the uplink, at the UE 450, a transmit processor 464 may receive andprocess data (e.g., for the physical uplink shared channel (PUSCH)) froma data source 462 and control information (e.g., for the physical uplinkcontrol channel (PUCCH)) from the controller/processor 480. Theprocessor 464 may also generate reference symbols for a referencesignal. The symbols from the transmit processor 464 may be precoded by aTX MIMO processor 466 if applicable, further processed by the modulators454 a through 454 r (e.g., for SC-FDM, etc.), and transmitted to thebase station 410. At the base station 410, the uplink signals from theUE 450 may be received by the antennas 434, processed by thedemodulators 432, detected by a MIMO detector 436 if applicable, andfurther processed by a receive processor 438 to obtain decoded data andcontrol information sent by the UE 450. The processor 438 may providethe decoded data to a data sink 439 and the decoded control informationto the controller/processor 440. The base station 410 can send messagesto other base stations, for example, over an X2 interface 441.

The controllers/processors 440 and 480 may direct the operation at thebase station 410 and the UE 450, respectively. The processor 440/380and/or other processors and modules at the base station 410/UE 450 mayperform or direct the execution of the functional blocks illustrated inmethod flow chart FIG. 9 and/or other processes for the techniquesdescribed herein. A scheduler 444 may schedule UEs for data transmissionon the downlink and/or uplink. The memories 442 and 482 may store dataand program codes for the base station 410 and the UE 450, respectively.For example, the memory 482 of the UE 450 may store a measurementreporting module 491, which, when executed by the controller/processor480, configures the UE 450 to report inter-RAT and/or intra-RATmeasurements. For another example, the memory 442 of the base station410 may store a handover management module 421, which, when executed bythe controller/processor 440, configures the base station 410 to send ordelay sending handover commands

FIG. 5 illustrates exemplary network coverage areas. In particular, thegeographical area 500 includes RAT-1 cells 502 and RAT-2 cells 504. Inone example, the RAT-1 cells are LTE cells and the RAT-2 cells are 2G or3G cells. However, those skilled in the art will appreciate that othertypes of radio access technologies may be utilized within the cells. Auser equipment (UE) 506 may move from one cell, such as a RAT-1 cell502, to another cell, such as a RAT-2 cell 504 The movement of the UE506 may trigger a handover or a cell reselection. Movement betweendifferent types of RATs is denoted by the term inter-RAT. Movementwithin a same RAT is denoted as intra-RAT.

The handover or cell reselection may be performed when the UE moves froma coverage area of a first RAT to the coverage area of a second RAT, orvice versa. A handover or cell reselection may also be performed whenthere is a coverage hole or lack of coverage in one network or whenthere is traffic balancing between a first RAT and the second RATnetworks. As part of that handover or cell reselection process, while ina connected mode with a first system (e.g., TD-SCDMA) a UE may bespecified to perform a measurement of a neighboring cell (such as GSMcell). For example, the UE may measure the neighbor cells of a secondnetwork for signal strength, frequency channel, and base stationidentity code (BSIC). The UE may then connect to the strongest cell ofthe second network. Such measurement may be referred to as inter-radioaccess technology (IRAT) measurement.

The UE may send a serving cell a measurement report indicating resultsof the inter-RAT (IRAT) measurement performed by the UE. The servingcell may then trigger a handover of the UE to a new cell in the otherRAT based on the measurement report. The measurement may include aserving cell signal strength, such as a received signal code power(RSCP) for a pilot channel (e.g., primary common control physicalchannel (PCCPCH)). The signal strength is compared to a serving systemthreshold. The serving system threshold can be indicated to the UEthrough dedicated radio resource control (RRC) signaling from thenetwork. The measurement may also include a neighbor cell receivedsignal strength indicator (RSSI). The neighbor cell signal strength canbe compared with a neighbor system threshold. Before handover or cellreselection, in addition to the measurement processes, the base stationIDs (e.g., BSICs) are confirmed and re-confirmed.

Ongoing communication on the UE may be handed over from the first RAT toa second RAT based on measurements performed on the second RAT. Forexample, the UE may tune away to the second RAT to perform themeasurements. Examples of ongoing communications on the UE includecommunications according to a single radio voice call continuity (SRVCC)procedure. SRVCC is a solution aimed at providing continuous voiceservices on packet-switched networks (e.g., LTE networks). In the earlyphases of LTE deployment, when UEs running voice services move out of anLTE network, the voice services can continue in the legacycircuit-switched (CS) domain using SRVCC, ensuring voice servicecontinuity. SRVCC is a method of inter-radio access technology (IRAT)handover. SRVCC enables smooth session transfers from voice overinternet protocol (VoIP) over the IP multimedia subsystem (IMS) on theLTE network to circuit-switched services in the universal terrestrialradio access network (UTRAN) or GSM enhanced date rates for GSMEvolution (EDGE) radio access network (GERAN).

LTE coverage is limited in availability. When a UE conducting apacket-switched voice call (e.g., voice over LTE (VoLTE) call) leavesLTE coverage or when the LTE network is highly loaded, SRVCC may be usedto maintain voice call continuity from a packet-switched (PS) call to acircuit-switched call during IRAT handover scenarios. SRVCC may also beused, for example, when a UE has a circuit-switched voice preference(e.g., circuit-switched fallback (CSFB)) and packet-switched voicepreference is secondary if combined attach fails. The evolved packetcore (EPC) may send an accept message for packet-switched attach inwhich case a VoIP/IMS capable UE initiates a packet-switched voice call.

A UE may perform an LTE serving cell measurement. When the LTE servingcell signal strength or quality is below a threshold (meaning the LTEsignal may not be sufficient for an ongoing call), the UE may report anevent 2A (change of the best frequency). In response to the measurementreport, the LTE network may send radio resource control (RRC)reconfiguration messages indicating 2G/3G neighbor frequencies. The RRCreconfiguration message also indicates event B1 (neighbor cell becomesbetter than an absolute threshold) and/or B2 (a serving RAT becomesworse than a threshold and the inter-RAT neighbor become better thananother threshold). The LTE network may also allocate LTE measurementgaps. For example, the measurement gap for LTE is a 6 ms gap that occursevery 40 or 80 ms. The UE uses the measurement gap to perform 2G/3Gmeasurements and LTE inter-frequency measurements. When the LTE eNode Breceives the event B1 report from the UE, the LTE eNode B may initiatethe SRVCC procedure. The SRVCC procedure may be implemented in awireless network, such as the wireless network of FIG. 6.

FIG. 6 is a block diagram illustrating a wireless communication network600 in accordance with aspects of the present disclosure. Referring toFIG. 6, the wireless communication network may include a visited network602 and a home network 622. The visited network 602 may include multipleservice areas. For example, as shown in FIG. 6, without limitation, thevisited network 602 may include an LTE service area 610 and a UMTSservice area 612. A first UE (UE1) located in the LTE service area 610may conduct a voice call with a second UE (UE2), which is located in thehome network 622. In one aspect, UE1 may conduct a voice call (e.g., aPS call or VoLTE) with UE2 via the access transfer gateway (ATGW) 618.

When UE1 leaves the LTE service area 610, the LTE serving cell (eNodeB604) signal strength or signal quality may fall below a threshold. Assuch, UE1 may report an event 2A. In turn, the eNode B 604 may providean RRC connection reconfiguration message to UE1. The RRC connectionreconfiguration message may include measurement configurationinformation such as the LTE measurement gap allocation. For example, theLTE gap allocation may be such that a 6 ms measurement gap occurs every40 ms.

Accordingly, UE1 may conduct the IRAT and inter-frequency measurementsand provide a corresponding measurement report to the eNode B 604, whichmay initiate the handover of coverage to the Node B 606 of the UMTSservice area 612. The mobility management entity (MME) 608 may initiatean SRVCC procedure for the handover. A switch procedure may be initiatedto transfer the voice call to a circuit-switched network. An access pathswitching request is sent via the mobile switching center (MSC) 614,which routes the voice call to UE2 via the access transfer gateway(ATGW) 618. Thereafter, the call between UE1 and UE2 may be transferredto a circuit-switched call. The various communication links or paths arerepresented by solid and different dashed lines. The communication pathsinclude circuit-switched (CS) path after handover (HO), packet-switchedpath before handover, session initiation protocol (SIP) signal path,session initiation protocol signal path for a second UE (UE2) and acommunication plane (C-plane) path.

An undesirable event may occur when the LTE serving or a different intraor inter-frequency neighbor cells are weak but relatively better thanthe signal quality of the current serving cell and the UE still performsthe handover to the target cell. When the UE performs handover to thetarget cell after receiving a handover command, in these cases, a callfailure may occur.

FIG. 7 is an exemplary call flow diagram 700 illustrating a signalingprocedure in accordance with aspects of the present disclosure. At time714, a user equipment (UE) 702 is in an original operation mode, such asa connected mode or a dedicated channel (DCH) mode with apacket-switched (PS) RAT (e.g., LTE). For example, in one aspect, the UEmay conduct a voice call (e.g., a PS call or VoLTE) via the serving LTEeNodeB 704.

At time 716, the serving LTE eNodeB 704 sends a first radio resourcecontrol (RRC) connection reconfiguration message to a UE 702. The firstRRC connection configuration message may include the measurementconfiguration with information about the measurement gap resources. Forexample, the first RRC connection configuration message may be directedto inter-frequency handover measurements and events, such as event 2A.The event 2A based RRC connection configuration message may result fromthe UE leaving a coverage area of the serving LTE eNodeB 704, at time718. At time 720, the UE 702 sends an event 2A measurement report to theserving LTE eNodeB 704.

In some aspects, the serving LTE eNodeB 704 sends a second RRCconnection reconfiguration message to the UE 702. The second RRCconnection configuration message may also include the measurementconfiguration with information about the measurement gap resources. Forexample, the second RRC connection configuration message may be directedto event B1 when an inter-RAT neighbor becomes better than a threshold.The second RRC connection configuration message may also be directed toevent B2 when a serving RAT becomes worse than a threshold and theinter-RAT neighbor become better than another threshold. At time 724,the UE 702 performs the inter-RAT measurement. At time 726, the UE 702sends an event B1/B2 measurement report to the serving LTE eNodeB 704.

The serving LTE eNodeB 704 provides an indication of whether handover isdesirable (e.g., with a first reported cell) to a mobility managemententity (MME) 706, at time 728. In turn, at time 730, the mobilitymanagement entity 706 initiates SRVCC for circuit-switched (CS) andpacket-switched (PS) handovers. For example, the mobility managemententity 706 transmits a packet-switched to circuit-switched handoverrequest to an SRVCC mobile switching center (MSC) server 708. In turn,at time 732, the SRVCC mobile switching center server 708 begins aninternet protocol multimedia subsystem (IMS) service continuityprocedure with an internet protocol multimedia subsystem 712. Theprocedure may include an internet protocol multimedia subsystem sessiontransfer procedure or a path switch procedure. For example, the pathswitch procedure includes switching a voice communication path from LTEto 2G or 3G.

At time 734, the SRVCC mobile switching center server 708 beginscircuit-switched/packet-switched handover preparation with a targetradio network controller (RNC)/base station subsystem (BSS) 710. At time736, the SRVCC mobile switching center server 708 sends a handoverresponse message to the mobility management entity 706. The handoverresponse message may include a packet-switched to circuit-switchedhandover request acknowledgment (ACK). At time 738, the mobilitymanagement entity 706 sends a message to the eNode B 704 including ahandover command. At time 740, the eNode B 704 provides a handovercommand to the UE 702 instructing the UE to handover communications fromthe eNode B 704 to the target radio network controller (RNC)/basestation subsystem (BSS) 710.

In the handover procedure, the target cell is available and the UE 702is not prematurely handed over to the target cell. Accordingly, afterreceiving the handover command at time 760, a handover complete messageis sent to the target radio network controller (RNC)/base stationsubsystem (BSS) 710. At time 762, the SRVCC mobile switching centerserver 708 completes circuit-switched/packet-switched handover with themobility management entity 706. At time 764, the circuit-switched voicecall is established with the target radio network controller (RNC)/basestation subsystem (BSS) 710.

Inter-RAT and Intra-RAT Measurement Reporting and Handover

During a VoLTE (voice over LTE) call, a UE may continuously perform LTEserving cell measurements. As discussed above, when the signal qualityof the LTE serving cell falls below a predetermined threshold, the UEmay report an event A2. In response to the report, the LTE serving cellsends radio resource control (RRC) reconfiguration messages indicating2G/3G neighbor frequencies, and an event B1 threshold. The LTE servingcell may also allocate LTE measurement gaps. The UE uses the measurementgaps to perform the 2G/3G measurements and LTE inter-frequencymeasurements. When an LTE nodeB receives a B1 event report from the UEand when the signal quality of the target 2G/3G cell is below thethreshold indicated in the B1 event, the LTE nodeB may initiate an SRVCCinter-RAT handover procedure, as indicated at time 728 of FIG. 7.

The LTE network may also configure intra- and inter-frequencymeasurements and reports, based on the event A3. The event A3 occurswhen the neighbor cell signal quality is above the serving cell signalquality by an offset indicated by a network, and lasts for a time totrigger duration. The UE sends a measurement report for an A3 event,which triggers handover. That is, the UE may perform an LTE intra and/orinter-frequency neighbor cell measurement. In previous approaches, whenthe neighbor cell signal quality is above the LTE serving cell, the UEsends a measurement report which in turn triggers an intra-LTE handover.

The intra-RAT and -inter-RAT measurement reports are configured to runin parallel independently, each with a time to trigger (TTT) timer. Whena TTT timer expires, the UE sends the measurement report correspondingto the expired timer. In some scenarios, the UE may handover to a weakLTE neighbor cell and miss the chance to handover to a good 2G/3G cellin the SRVCC procedure. This may result in a VoLTE call being dropped.

Aspects of the present disclosure are directed to reducing call drops inLTE before an SRVCC procedure. In particular, the UE may delay sendingintra- or inter-RAT measurement reports based on a combination offactors, such as the LTE serving cell signal quality, the neighbor cellsignal quality and/or the current status of a call setup. Those skilledin the art will appreciate the term “signal quality” is non-limiting.Signal quality is intended to cover any type of signal metric, such as,but not limited to signal strength, signal power, signal quality, etc.

In one example, when the quality of the LTE serving cell signal is belowan absolute threshold (e.g., a first UE-defined threshold) and thequality of the neighbor cell signal is below another absolute threshold(e.g., a second UE-defined threshold), the UE may delay sending anintra-RAT (e.g., intra-LTE) measurement report for a predefined period(e.g., measurement report holding time period). Further, the UE maydelay sending the intra-RAT measurement report even when thecorresponding TTT timer has expired. In one aspect, the UE sends theintra-RAT measurement report when the signal qualities of the LTEserving cell and the neighbor cell are both above the predefinedabsolute thresholds (e.g., the first UE-defined threshold, the secondUE-defined threshold).

Additionally, the UE may delay sending the inter-RAT measurement reportfor another predefined period of time (e.g., the measurement reportholding time period) even after the corresponding TTT timer has expired.The UE may send an inter-RAT measurement report if the LTE call setup iscompleted. The predefined absolute thresholds and the predefinedmeasurement report holding time periods may be adjusted based on factorssuch as, but not limited to: a UE speed, a UE receiver performance, aserving cell radio frequency (RF) variation trend, and applicationquality of service (QoS) specifications, among others.

FIG. 8 is a flow diagram illustrating an example flow diagram 800 forinter-RAT and intra-RAT measurement reporting according to aspects ofthe present disclosure. The flow diagram 800 is for illustrationpurposes only and other alternative aspects of the decision process formeasurement reports are certainly possible.

At block 802, a call is initiated by the UE. In the following example,an LTE voice call is discussed, however, the present disclosure is notso limited. For example, voice over WLAN (wireless local area network),video over LTE, video over WLAN, etc. is also contemplated. At block804, the UE determines whether TTT timers have expired. In particular,the UE monitors a time to trigger (TTT) timer for an inter-RATmeasurement and a TTT timer for the intra-RAT measurement report. In oneexample aspect, the two timers may run independently. One of the timersmay expire before the other, or at the same time.

According to one aspect of the present disclosure, when the inter-RATmeasurement report TTT timer expires, the UE checks the voice call setupstatus, at block 806 and determines whether the setup is complete. Ifthe UE determines the call setup is not complete, the UE may delaysending the inter-RAT measurement report for a predetermined holdingtime period, as shown in block 808. When the predetermined holding timeperiod expires, the UE may send the inter-RAT measurement report, atblock 810, to the serving base station.

If the UE determines, at block 806, the voice call setup is complete,the UE may send the inter-RAT measurement report without any delay, totrigger an inter-RAT handover to a 2G/3G network. At block 812, the UEmay adjust the inter-RAT measurement report holding time period based onfactors such as a UE speed, a current serving cell radio frequency (RF)variation trend, a number of inter-RAT neighbor cells, the applicationQoS specifications and a percentage of call setup completion. In theabove example, the LTE call setup status is a factor for determiningwhether to delay sending an inter-RAT measurement report.

Referring back to block 804, when the intra-RAT measurement report TTTtimer expires, the UE may evaluate cell signal qualities. In particular,at block 822, the UE determines whether the current LTE serving cellsignal quality is above a first UE-defined threshold and whether aneighbor cell signal quality is above a second UE-defined threshold. Ifthe UE determines either or both of the signal qualities are below theabsolute threshold(s), the UE proceeds to block 824 and delays sendingthe intra-RAT measurement report for a predefined intra-RAT measurementreport holding time period. When the intra-RAT measurement reportholding time period expires, the UE sends the intra-RAT measurementreport to the serving base station without further delay. Optionally,the UE may delay sending the intra-RAT measurement report when thedifference in signal quality between the serving cell and the neighborcell is below a relative threshold.

If the UE determines at block 822 that both the signal qualities areabove the absolute thresholds, the UE proceeds to block 826, and sendsthe intra-RAT measurement report without delay. Optionally, the UE maysend the intra-RAT measurement report, without delay, when the relativedifference in signal quality between the serving cell and the neighborcell is above a relative threshold.

At block 828, the UE adjusts the first and the second absolute signalquality thresholds. The adjustment may be based on a UE speed, a UEreceiver performance and a serving cell radio frequency (RF) variationtrend, and/or application quality of service (QoS) specifications. TheUE may also adjust the intra-RAT measurement report holding time periodbased on UE speed, the current serving cell RF variation trend, a numberof intra-frequency neighbors, and/or the application QoS specifications.

FIG. 9 is a flow diagram illustrating a method 900 for intra-RAT andinter-RAT measurement reporting during a call setup, according toaspects of the present disclosure. At block 902, the UE in an LTE voicecall setup may determine whether to delay sending an inter-RATmeasurement report and/or an intra-RAT measurement report, after thecorresponding TTT timer has expired. The determination may be based atleast in part on a status of a call setup. Optionally, the determinationmay also consider the signal quality of a current serving cell and/orthe signal quality of a neighbor cell. The determination may also bebased on whether the current serving cell of a first RAT or a neighborcell of a second RAT provides a better QoS to an active service orapplication running at the UE.

In one example aspect, determining whether to delay sending an inter-RATmeasurement report and/or intra-RAT measurement report may be based on astatus of the LTE voice call setup. For example, the voice call setupmay be in a pre-alerting stage, alerting stage, before default bearerestablishment for signaling stage, after default bearer establishmentfor signaling stage, before dedicated bearer establishment for trafficstage or after dedicated bearer establishment for traffic stage. If thevoice call setup is in a stage other than the after dedicated bearerestablishment stage, the UE may determine to delay send the inter-RATmeasurement report. The inter-RAT measurement report may trigger aninter-RAT handover from the current LTE network to a 2G/3G network. Thevoice call may be dropped at the 2G/3G network if the LTE call setup isnot completed when the handover takes place. The current status of thecall setup may include alerting, pre-alerting, before default bearerestablishment for signaling (e.g. voice over LTE IMS signaling), afterdefault bearer establishment for signaling, before dedicated bearerestablishment for traffic and after dedicated bearer establishment fortraffic.

In another example aspect, determining whether to delay sending theintra-LTE measurement report may be based on a first UE-defined absolutethreshold for the neighbor cell signal quality and a second UE-definedabsolute threshold for the current serving cell signal quality. In oneexample where both the serving LTE cell signal quality and LTE neighborcell signal quality are weak, but the neighbor LTE cell signal qualityis relatively better than the current serving cell signal quality, anintra-RAT (e.g., intra-LTE) measurement report may trigger a handover tothe weak neighbor cell. The call may be dropped because of the weaksignal quality of the neighbor cell.

In another example, when determining whether to delay sending ameasurement report, the UE considers whether the serving LTE cell signalquality is above the first UE-defined absolute threshold and theneighbor LTE cell is above a second UE-defined absolute threshold. Whenthe signal quality of each is above the associated threshold, the UE maydetermine not to delay sending the intra-RAT measurement report withoutany delay.

At block 904, the UE delays sending the inter-RAT measurement reportand/or the intra-RAT measurement report based on the determination.Further, the UE delays sending the measurement report for a particularamount of time (e.g., inter-RAT measurement report holding time period,intra-RAT measurement report holding time period).

In another example, the UE delays sending an intra-RAT measurementreport for the intra-RAT measurement report holding time period. Duringthe intra-RAT measurement report holding time period, the conditionsthat cause the UE to delay sending the intra-RAT measurement report mayhave changed. For example, the LTE neighbor cell signal quality and thecurrent serving cell signal quality may both become higher than thecorresponding UE-defined absolute thresholds. In yet another example,the UE delays sending the intra-RAT measurement report when a signalquality difference between the current serving cell and an intra-RATneighbor cell is below a UE-defined relative threshold.

At block 904, delaying sending the inter-RAT measurement report by theUE may include reducing a frequency of inter-RAT measurements when atleast one of the UE, the serving network and the target network does notsupport the inter-RAT handover while in the current status of the callsetup.

At block 906, the UE sends the intra-RAT measurement report, once theintra-RAT measurement report holding time period expires. The UE maysend the inter-RAT measurement report when the inter-RAT measurementreport holding time period expires. In another example aspect, the UEmay also send the intra-RAT measurement report or inter-RAT measurementreport before the corresponding measurement report holding time periodsexpire, when the conditions that cause the UE to delay sending themeasurement report have changed before the measurement report holdingtime periods expire. For example, if the neighbor cell signal qualityand the current serving cell signal quality become above the respectiveUE-defined absolute thresholds, the UE may send the measurement reportwithout waiting for the measurement report holding time period expires.For another example, the UE sends the intra-RAT measurement report whena signal quality difference between the current serving cell andintra-RAT neighbor cell is above a relative threshold.

At block 906, the UE may optionally send the inter-RAT measurementreport when a current call is in the call setup or when at least one ofthe UE, a serving network or a target network supports an inter-RAThandover during the call setup, and a signal quality of each of theserving cell and an intra-RAT neighbor cell become lower than the firstUE-defined absolute threshold.

In one example, the UE may optionally adjust the intra-RAT measurementreport holding time period, as shown in block 908. The adjustment may bebased on a UE speed, a UE receiver performance and a serving cell radiofrequency (RF) variation trend, and/or application quality of service(QoS) specifications. For example, if the UE speed is high, theintra-RAT measurement report holding time period may be set relativelyshort because the UE may move out of the serving cell within arelatively short period of time. In another example, if the UE receiveperformance is poor, the intra-RAT measurement report holding timeperiod may be set relatively long because it may take longer for the UEto receive correct transmissions. In yet another example, if the servingcell radio frequency (RF) variation trend indicates that serving cellsignal quality is becoming worse and the neighbor cell radio frequency(RF) variation trend indicates the neighbor cell signal quality isbecoming better, the intra-RAT measurement report holding time periodmay be set shorter, so the UE may be handed over to the neighbor cellfaster.

At block 908, the UE may also optionally adjust the inter-RATmeasurement report holding time period based on a UE speed, a UEreceiver performance, a percentage of call setup completion and/orapplication quality of service (QoS) specifications. For example, if theUE speed is high, the inter-RAT measurement report holding time periodmay be set relatively short because the UE may move out of this servingRAT within a relatively short period of time. In another example, if theUE receiver performance is poor, the inter-RAT measurement reportholding time period may be set relatively long because it may takelonger for the UE to receive correct transmissions. In yet anotherexample, if the percentage of the call setup completion is high, theinter-RAT measurement report holding time period may be set relativelyshort because the call setup is expected to be completed soon.

Additionally, in another optional example, the UE may optionally adjusta first UE-defined threshold for the current serving cell signal qualityand a second UE-defined threshold for the neighbor cell signal quality,as shown in optional block 910. The optional adjustment may be based ona UE speed, a UE receiver performance and/or a serving cell radiofrequency (RF) variation trend, and application quality of service (QoS)specifications, among others. For example, if the UE speed is high, thefirst UE-defined threshold may be set relatively low so it may be easierto cause the intra-RAT measurement report to be sent, because the UE maymove out of this serving cell within a relatively short period of time.

In another example, if the UE receive performance is poor, the firstUE-defined threshold may be set relatively low so that it would not taketoo longer for the intra-RAT measurement report to be triggered. In yetanother example, if the serving cell radio frequency (RF) variationtrend indicates that serving cell signal quality is becoming worse andthe neighbor cell radio frequency (RF) variation trend indicates theneighbor cell signal quality is becoming better, the first UE-definedthreshold and the second UE-defined threshold may be set relatively low,so the UE may be handed over to the neighbor cell faster.

In practice, one or more steps shown in illustrative method 900 may becombined with other steps, performed in any suitable order, performed inparallel (e.g., simultaneously or substantially simultaneously), orremoved.

FIG. 10 is a flow diagram illustrating a method 1000 for intra-RAT andinter-RAT handover at a network during a call setup, according toaspects of the present disclosure. At block 1002, the network in an LTEvoice call setup may determine whether to delay sending an inter-RAThandover command and/or an intra-RAT handover command to a UE. Thedetermination may be based at least in part on a current status of thecall setup. Optionally, the determination may also consider the signalquality of a current serving cell and/or the signal quality of aneighbor cell reported from the UE. The network may be a serving networkor a target network for handover.

In one example aspect, determining whether to delay sending an inter-RAThandover command and/or intra-RAT handover command may be based on acurrent status of the LTE voice call setup. For example, the voice callsetup may be in a call setup status such as a pre-alerting, alerting,before default bearer establishment for signaling, after default bearerestablishment for signaling, before dedicated bearer establishment fortraffic or after dedicated bearer establishment for traffic. If thevoice call setup is in a stage other than the after dedicated bearerestablishment for traffic, the network may determine to delay send theinter-RAT handover command. The voice call may be dropped at the 2G/3Gnetwork if the LTE call setup is not completed when the inter-RAThandover takes place.

In another example aspect, determining whether to delay sending theintra-LTE handover command may be based on a first network-definedabsolute threshold for the neighbor cell signal quality and a secondnetwork-defined absolute threshold for the current serving cell signalquality. In one example where the serving LTE cell signal quality andLTE neighbor cell signal quality, as reported from the UE, are bothweak, but the neighbor LTE cell signal quality is relatively better thanthe current serving cell signal quality, the network may send anintra-RAT (e.g., intra-LTE) handover to the weak neighbor cell. The callmay be dropped because of the weak signal quality of the neighbor cell.

In another example, when determining whether to delay sending thehandover command to the UE, the network considers whether the servingLTE cell signal quality, as reported from the UE, is above the firstnetwork-defined absolute threshold and the neighbor LTE cell signalquality is above a second network-defined absolute threshold. When thesignal quality of each is above the associated threshold, the networkmay determine not to delay sending the intra-RAT handover command.

At block 1004, the network delays sending the inter-RAT handover commandand/or the intra-RAT handover command based on the above determination.Further, the network delays sending the handover command for aparticular amount of time (e.g., inter-RAT handover holding time period,intra-RAT handover holding time period).

In another example, the network delays sending an intra-RAT handovercommand for the intra-RAT handover holding time period. During theintra-RAT handover holding time period, the conditions that cause thenetwork to delay sending the intra-RAT handover command may havechanged. For example, the LTE neighbor cell signal quality and thecurrent serving cell signal quality, as reported from the UE, may bothbecome higher than the corresponding network-defined absolutethresholds. In yet another example, the network delays sending theintra-RAT handover command when a signal quality difference between thecurrent serving cell and an intra-RAT neighbor cell is below anetwork-defined relative threshold (e.g., a first network-definedrelative threshold).

At block 1006, the network sends the intra-RAT handover command, oncethe intra-RAT handover holding time period expires. The network may sendthe inter-RAT handover command when the inter-RAT handover holding timeperiod expires. In another example aspect, the network may also send theintra-RAT handover command or inter-RAT handover command before thecorresponding handover holding time periods expire, when the conditionsthat caused the network to delay sending the handover commands havechanged before the handover holding time periods expire. For example, ifthe neighbor cell signal quality and the current serving cell signalquality, as reported from the UE, become above the respectivenetwork-defined absolute thresholds, the network may send the handovercommand without waiting for the handover holding time period expires.For another example, the network sends the intra-RAT handover commandwhen a signal quality difference between the current serving cell andintra-RAT neighbor cell, as reported from the UE, is above a relativethreshold (e.g., a second network-defined relative threshold).

At block 1006, the network may optionally send the inter-RAT handovercommand when the call setup changes to a new current status in whichboth the UE and the network support the inter-RAT handover and/or asignal quality of each of the serving cell and an intra-RAT neighborcell become lower than the first network-defined absolute threshold.

In one example, the network may optionally adjust the intra-RAT handoverholding time period, as shown in block 1008. The adjustment may be basedon a UE speed as measured at the network, a current serving cell radiofrequency variation trend, and/or application quality of service (QoS)specifications. For example, if the UE speed is high, the intra-RAThandover holding time period may be set relatively short because the UEmay move out of the serving cell within a relatively short period oftime. In another example, if the serving cell radio frequency (RF)variation trend, as reported from the UE, indicates that serving cellsignal quality is becoming worse and the neighbor cell radio frequencyvariation trend indicates the neighbor cell signal quality is becomingbetter, the intra-RAT handover holding time period may be set shorter,so the network may have the UE handed over to the neighbor cell faster.

At block 1008, the network may also optionally adjust the inter-RAThandover holding time period based on a UE speed, a percentage of callsetup completion and/or application quality of service (QoS)specifications. For example, if the UE speed is high, the inter-RATmeasurement report holding time period may be set relatively shortbecause the UE may move out of this serving RAT within a relativelyshort period of time. The UE speed may be measured by the network, basedon uplink signals from the UE, the signals such as uplink soundingreference signals, uplink pilot channels, and demodulation referencesignals. In yet another example, if the percentage of the call setupcompletion is high, the inter-RAT handover holding time period may beset relatively short because the call setup is expected to be completedsoon.

Additionally, in another optional example, at block 1010, the networkmay adjust a first network-defined absolute threshold for the currentserving cell signal quality and a second network-defined threshold forthe neighbor cell signal quality, as shown in optional block 1010. Theoptional adjustment may be based on a UE speed, and/or a serving cellradio frequency (RF) variation trend, and application quality of service(QoS) specifications, among others. For example, if the UE speed ishigh, the first network-defined threshold may be set relatively low soit may be easier to trigger the handover command to be sent, because theUE may move out of this serving cell within a relatively short period oftime.

In yet another example, if the serving cell radio frequency (RF)variation trend, as reported from the UE, indicates that serving cellsignal quality is becoming worse and the neighbor cell radio frequency(RF) variation trend indicates the neighbor cell signal quality isbecoming better, the first network-defined absolute threshold and thesecond network-defined absolute threshold may be set relatively low, sothe handover command may be sent to cause the UE be handed over to theneighbor cell faster.

In practice, one or more steps shown in illustrative method 1000 may becombined with other steps, performed in any suitable order, performed inparallel (e.g., simultaneously or substantially simultaneously), orremoved.

FIG. 11 is a block diagram illustrating an example of a hardwareimplementation for an apparatus 1100 employing a processing system 1114with different modules/means/components for fast return failure handlingin a high speed scenario in an example apparatus according to one aspectof the present disclosure. The processing system 1114 may be implementedwith a bus architecture, represented generally by the bus 1124. The bus1124 may include any number of interconnecting buses and bridgesdepending on the specific application of the processing system 1114 andthe overall design constraints. The bus 1124 links together variouscircuits including one or more processors and/or hardware modules,represented by the processor 1122 the modules 1102, 1104, 1106 and thenon-transitory computer-readable medium 1126. The bus 1124 may also linkvarious other circuits, such as timing sources, peripherals, voltageregulators, and power management circuits, which are well known in theart, and therefore, will not be described any further.

The apparatus includes a processing system 1114 coupled to a transceiver1130. The transceiver 1130 is coupled to one or more antennas 1120. Thetransceiver 1130 enables communicating with various other apparatus overa transmission medium. The processing system 1114 includes a processor1122 coupled to a non-transitory computer-readable medium 1126. Theprocessor 1122 is responsible for general processing, including theexecution of software stored on the computer-readable medium 1126. Thesoftware, when executed by the processor 1122, causes the processingsystem 1114 to perform the various functions described for anyparticular apparatus. The computer-readable medium 1126 may also be usedfor storing data that is manipulated by the processor 1122 whenexecuting software.

The processing system 1114 includes a determining module 1102 fordetermining whether to delay sending an inter-RAT and/or intra-RATmeasurement report. The processing system 1114 also includes ameasurement module 1104 for sending and delaying sending of measurementreports. The processing system 1114 may also include an adjustmentmodule 1106 for adjusting a measurement report holding time period andan absolute signal quality threshold. The modules 1102, 1104 and 1106may be software modules running in the processor 1122, resident/storedin the computer-readable medium 1126, one or more hardware modulescoupled to the processor 1122, or some combination thereof Theprocessing system 1114 may be a component of the UE 450 of FIG. 4 andmay include the memory 482, and/or the controller/processor 480.

In one configuration, an apparatus, such as a UE 450, is configured forwireless communication including means for determining whether to delaysending an inter-RAT or intra-RAT measurement report. In one aspect, thedetermining means may be the antennas 452, the receive processor 458,the controller/processor 480, the memory 482, the measurement reportingmodule 491, the determining module 1102, and/or the processing system1114 configured to perform the functions recited by the determiningmeans. In one configuration, the means and functions correspond to theaforementioned structures. In another aspect, the aforementioned meansmay be a module or any apparatus configured to perform the functionsrecited by the determining means.

The UE 450 is also configured to include means for delaying sending themeasurement report. In one aspect, the delaying means may include theantennas 452, the transmit processor 464, the controller/processor 480,the memory 482, the measurement reporting module 491, the measurementmodule 1104, and/or the processing system 1114 configured to perform thefunctions recited by the delaying means. In one configuration, the meansand functions correspond to the aforementioned structures. In anotheraspect, the aforementioned means may be a module or any apparatusconfigured to perform the functions recited by the delaying means.

The UE 450 is also configured to include means for sending themeasurement report. In one aspect, the sending means may include theantennas 452, the transmit processor 464, the controller/processor 480,the memory 482, the measurement reporting module 491, the measurementmodule 1104, and/or the processing system 1114 configured to perform thefunctions recited by the delaying means. In one configuration, the meansand functions correspond to the aforementioned structures. In anotheraspect, the aforementioned means may be a module or any apparatusconfigured to perform the functions recited by the sending means.

The UE 450 is also configured to include means for adjusting ameasurement report holding time period and an absolute signal qualitythreshold. In one aspect, the adjusting means may include the antennas452, the receive processor 458, the transmit processor 464, thecontroller/processor 480, the memory 482, the measurement reportingmodule 491, the measurement module 1104, the adjustment module 1106and/or the processing system 1114 configured to perform the functionsrecited by the switching means. In one configuration, the means andfunctions correspond to the aforementioned structures. In anotheraspect, the aforementioned means may be a module or any apparatusconfigured to perform the functions recited by the adjusting means.

FIG. 12 is a block diagram illustrating an example of a hardwareimplementation for an apparatus 1200 employing a processing system 1214with different modules/means/components for fast return failure handlingin a high speed scenario in an example apparatus according to one aspectof the present disclosure. The processing system 1214 may be implementedwith a bus architecture, represented generally by the bus 1224. The bus1224 may include any number of interconnecting buses and bridgesdepending on the specific application of the processing system 1214 andthe overall design constraints. The bus 1224 links together variouscircuits including one or more processors and/or hardware modules,represented by the processor 1222, the modules 1202, 1204, 1206 and thenon-transitory computer-readable medium 1226. The bus 1224 may also linkvarious other circuits, such as timing sources, peripherals, voltageregulators, and power management circuits, which are well known in theart, and therefore, will not be described any further.

The apparatus includes a processing system 1214 coupled to a transceiver1230. The transceiver 1230 is coupled to one or more antennas 1220. Thetransceiver 1230 enables communicating with various other apparatus overa transmission medium. The processing system 1214 includes a processor1222 coupled to a non-transitory computer-readable medium 1226. Theprocessor 1222 is responsible for general processing, including theexecution of software stored on the computer-readable medium 1226. Thesoftware, when executed by the processor 1222, causes the processingsystem 1214 to perform the various functions described for anyparticular apparatus. The computer-readable medium 1226 may also be usedfor storing data that is manipulated by the processor 1222 whenexecuting software.

The processing system 1214 includes a determining module 1202 fordetermining whether to delay sending an inter-RAT and/or intra-RAThandover command. The processing system 1214 also includes a handovermodule 1204 for sending and delaying sending of handover command. Theprocessing system 1214 may also include an adjustment module 1206 foradjusting a handover holding time period and an absolute signal qualitythreshold. The modules 1202, 1204 and 1206 may be software modulesrunning in the processor 1222, resident/stored in the computer-readablemedium 1226, one or more hardware modules coupled to the processor 1222,or some combination thereof. The processing system 1214 may be acomponent of the UE 450 of FIG. 4 and may include the memory 482, and/orthe controller/processor 480.

In one configuration, an apparatus, such as a base station 410, isconfigured for wireless communication including means for determiningwhether to delay sending a handover command to the UE. In one aspect,the determining means may be the antennas 434, the receive processor438, the controller/processor 440, the memory 442, the handovermanagement module 421, the determining module 1202, and/or theprocessing system 1214 configured to perform the functions recited bythe determining means. In one configuration, the means and functionscorrespond to the aforementioned structures. In another aspect, theaforementioned means may be a module or any apparatus configured toperform the functions recited by the determining means.

The base station 410 is also configured to include means for delayingsending the handover command. In one aspect, the delaying means mayinclude the antennas 434, the transmit processor 420, thecontroller/processor 440, the memory 442, the handover management module421, the handover module 1204, and/or the processing system 1214configured to perform the functions recited by the delaying means. Inone configuration, the means and functions correspond to theaforementioned structures. In another aspect, the aforementioned meansmay be a module or any apparatus configured to perform the functionsrecited by the delaying means.

The base station 410 is also configured to include means for sending thehandover command. In one aspect, the sending means may include theantennas 434, the transmit processor 420, the controller/processor 440,the memory 442, the handover management module 421, the handover module1204, and/or the processing system 1214 configured to perform thefunctions recited by the delaying means. In one configuration, the meansand functions correspond to the aforementioned structures. In anotheraspect, the aforementioned means may be a module or any apparatusconfigured to perform the functions recited by the sending means.

The base station 410 is also configured to include means for adjusting ahandover holding time period and an absolute signal quality threshold.In one aspect, the adjusting means may include the antennas 434, thereceive processor 438, the transmit processor 420, thecontroller/processor 440, the memory 442, the handover managementreporting module 491, the handover module 1204, the adjustment module1206 and/or the processing system 1214 configured to perform thefunctions recited by the switching means. In one configuration, themeans and functions correspond to the aforementioned structures. Inanother aspect, the aforementioned means may be a module or anyapparatus configured to perform the functions recited by the adjustingmeans.

Several aspects of a telecommunications system has been presented withreference to TD-SCDMA and LTE (in FDD, TDD, or both modes). As thoseskilled in the art will readily appreciate, various aspects describedthroughout this disclosure may be extended to other telecommunicationsystems, network architectures and communication standards, includingthose with high throughput and low latency such as 4G systems, 5Gsystems and beyond. By way of example, various aspects may be extendedto other systems, such as or LTE-advanced (LTE-A), W-CDMA, high speeddownlink packet access (HSDPA), high speed uplink packet access (HSUPA),high speed packet access plus (HSPA+) and TD-CDMA. Various aspects mayalso be extended to systems employing ultra mobile broadband (UMB), IEEE802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, ultra-wideband (UWB),Bluetooth, and/or other suitable systems. The actual telecommunicationstandard, network architecture, and/or communication standard employedwill depend on the specific application and the overall designconstraints imposed on the system.

Several processors have been described in connection with variousapparatuses and methods. These processors may be implemented usingelectronic hardware, computer software, or any combination thereofWhether such processors are implemented as hardware or software willdepend upon the particular application and overall design constraintsimposed on the system. By way of example, a processor, any portion of aprocessor, or any combination of processors presented in this disclosuremay be implemented with a microprocessor, microcontroller, digitalsignal processor (DSP), a field-programmable gate array (FPGA), aprogrammable logic device (PLD), a state machine, gated logic, discretehardware circuits, and other suitable processing components configuredto perform the various functions described throughout this disclosure.The functionality of a processor, any portion of a processor, or anycombination of processors presented in this disclosure may beimplemented with software being executed by a microprocessor,microcontroller, DSP, or other suitable platform.

Software shall be construed broadly to mean instructions, instructionsets, code, code segments, program code, programs, subprograms, softwaremodules, applications, software applications, software packages,routines, subroutines, objects, executables, threads of execution,procedures, functions, etc., whether referred to as software, firmware,middleware, microcode, hardware description language, or otherwise. Thesoftware may reside on a non-transitory computer-readable medium. Acomputer-readable medium may include, by way of example, memory such asa magnetic storage device (e.g., hard disk, floppy disk, magneticstrip), an optical disk (e.g., compact disc (CD), digital versatile disc(DVD)), a smart card, a flash memory device (e.g., card, stick, keydrive), random access memory (RAM), read only memory (ROM), programmableROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM),a register, or a removable disk. Although memory is shown separate fromthe processors in the various aspects presented throughout thisdisclosure, the memory may be internal to the processors (e.g., cache orregister).

Computer-readable media may be embodied in a computer-program product.By way of example, a computer-program product may include acomputer-readable medium in packaging materials. Those skilled in theart will recognize how best to implement the described functionalitypresented throughout this disclosure depending on the particularapplication and the overall design constraints imposed on the overallsystem.

It is to be understood that the specific order or hierarchy of steps inthe methods disclosed is an illustration of exemplary processes. Basedupon design preferences, it is understood that the specific order orhierarchy of steps in the methods may be rearranged. The accompanyingmethod claims present elements of the various steps in a sample order,and are not meant to be limited to the specific order or hierarchypresented unless specifically recited therein.

It is also to be understood that the term “signal quality” isnon-limiting. Signal quality is intended to cover any type of signalmetric, such as received signal code power (RSCP), reference signalreceived power (RSRP), reference signal received quality (RSRQ),received signal strength indicator (RSSI), signal to noise ratio (SNR),signal to interference plus noise ratio (SINR), etc.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but is to be accorded the full scope consistentwith the language of the claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” Unless specifically statedotherwise, the term “some” refers to one or more. As used herein,including in the claims, the term “and/or,” when used in a list of twoor more items, means that any one of the listed items can be employed byitself, or any combination of two or more of the listed items can beemployed. For example, if a composition is described as containingcomponents A, B, and/or C, the composition can contain A alone; B alone;C alone; A and B in combination; A and C in combination; B and C incombination; or A, B, and C in combination. Also, as used herein,including in the claims, “or” as used in a list of items (for example, alist of items prefaced by a phrase such as “at least one of” or “one ormore of”) indicates a disjunctive list such that, for example, a list of“at least one of A, B, or C” means A or B or C or AB or AC or BC or ABC(i.e., A and B and C). All structural and functional equivalents to theelements of the various aspects described throughout this disclosurethat are known or later come to be known to those of ordinary skill inthe art are expressly incorporated herein by reference and are intendedto be encompassed by the claims. Moreover, nothing disclosed herein isintended to be dedicated to the public regardless of whether suchdisclosure is explicitly recited in the claims. No claim element is tobe construed under the provisions of 35 U.S.C. §112, sixth paragraph,unless the element is expressly recited using the phrase “means for” or,in the case of a method claim, the element is recited using the phrase“step for.”

What is claimed is:
 1. A method of wireless communication at a userequipment (UE) during a call setup, comprising: determining whether todelay sending an inter-RAT (radio access technology) measurement reportor an intra-RAT measurement report based at least in part on a currentstatus of the call setup and whether both the UE and a network supportan inter-RAT handover while in the current status of the call setup, anetwork being a serving network or a target network; delaying sendingthe intra-RAT measurement report for an intra-RAT measurement reportholding time period and/or an inter-RAT measurement report for aninter-RAT measurement report holding time period based at least in parton the determination; and sending the intra-RAT measurement reportand/or the inter-RAT measurement report when the intra-RAT measurementreport holding time period and/or the inter-RAT measurement reportholding time period expire and/or the current status of the call setupchanges to the new current status of the call setup in which both the UEand the network support the inter-RAT handover.
 2. The method of claim1, in which determining is further based on at least one of: whether asignal quality of a current serving cell is above a first UE-definedabsolute threshold and whether the signal quality of a neighbor cell isabove a second UE-defined absolute threshold; and whether the currentserving cell of a first RAT or the neighbor cell of a second RATprovides a better QoS (quality of service) to an active service orapplication running at the UE.
 3. The method of claim 2, furthercomprising: adjusting the first UE-defined absolute threshold and/or thesecond UE-defined absolute threshold based at least in part on one of aUE speed, a UE receiver performance, a serving cell radio frequency (RF)variation trend, and application quality of service (QoS)specifications; and adjusting the inter-RAT measurement report holdingtime period and/or the intra-RAT measurement report holding time periodbased at least in part on one of the UE speed, a current serving cell RFvariation trend, a number of intra and/or inter-frequency neighbors,application QoS specifications and a percentage of call setupcompletion.
 4. The method of claim 2, further comprising: delayingsending the intra-RAT measurement report when the signal quality of thecurrent serving cell is above the first UE-defined absolute thresholdand an intra-RAT neighbor cell signal quality is below the secondUE-defined absolute threshold.
 5. The method of claim 2, furthercomprising: sending the intra-RAT measurement report when the signalquality of the current serving cell becomes lower than the firstUE-defined absolute threshold and the signal quality of an intra-RATneighbor cell becomes higher than the second UE-defined absolutethreshold.
 6. The method of claim 2, further comprising: sending theinter-RAT measurement report when both the UE and the network supportthe inter-RAT handover while in the current status of the call setup andthe signal quality of each of the current serving cell and an intra-RATneighbor cell become lower than the first UE-defined absolute threshold.7. The method of claim 2, further comprising: delaying sending theintra-RAT measurement report when a signal quality difference betweenthe current serving cell and an intra-RAT neighbor cell is below aUE-defined relative threshold; and sending the intra-RAT measurementreport when the signal quality difference between the current servingcell and an intra-RAT neighbor cell is above a relative threshold. 8.The method of claim 1, further comprising: delaying sending theinter-RAT measurement report when a current call is in the call setup orwhen at least one of the UE, the serving network or the target networkdo not support the inter-RAT handover during the call setup.
 9. Themethod of claim 1, further comprising: reducing a frequency of inter-RATmeasurements when at least one of the UE, the serving network and thetarget network does not support the inter-RAT handover while in thecurrent status of the call setup.
 10. The method of claim 1, in whichthe current status of the call setup comprises one of: alerting,pre-alerting, before default bearer establishment for signaling, afterdefault bearer establishment for signaling, before dedicated bearerestablishment for traffic and after dedicated bearer establishment fortraffic.
 11. An apparatus for wireless communication, comprising: amemory; a transceiver configured to communicate with a network; at leastone processor coupled to the memory, the at least one processor beingconfigured: to determine whether to delay sending an inter-inter-radioaccess technology (RAT) measurement report or an intra-RAT measurementreport based at least in part on a current status of a call setup andwhether a UE and a network support an inter-RAT handover while in thecurrent status of the call setup, a network being a serving network or atarget network; to delay sending the intra-RAT measurement report for anintra-RAT measurement report holding time period and/or the inter-RATmeasurement report for an inter-RAT measurement report holding timeperiod based at least in part on the determination; and to send theintra-RAT measurement report and/or the inter-RAT measurement reportwhen the intra-RAT measurement report holding time period and/or theinter-RAT measurement report holding time period expire and/or thecurrent status of the call setup changes to the new current status ofthe call setup in which both the UE and the network support theinter-RAT handover.
 12. The apparatus of claim 11, in which determiningis further based on at least one of: whether a signal quality of acurrent serving cell is above a first UE-defined absolute threshold andwhether the signal quality of a neighbor cell is above a secondUE-defined absolute threshold; and whether the current serving cell of afirst RAT or the neighbor cell of a second RAT provides a better QoS(quality of service) to an active service or application running at theUE.
 13. The apparatus of claim 12, in which the at least one processoris further configured: to adjust the first UE-defined absolute thresholdand/or the second UE-defined absolute threshold based at least in parton one of a UE speed, a UE receiver performance, a serving cell radiofrequency (RF) variation trend, and application quality of service (QoS)specifications; and to adjust the inter-RAT measurement report holdingtime period and/or the intra-RAT measurement report holding time periodbased at least in part on one of the UE speed, a current serving cell RFvariation trend, a number of intra and/or inter-frequency neighbors,application QoS specifications and a percentage of call setupcompletion.
 14. The apparatus of claim 12, in which the at least oneprocessor is further configured: to delay sending the intra-RATmeasurement report when the signal quality of the current serving cellis above the first UE-defined absolute threshold and the of an intra-RATneighbor cell signal quality is below the second UE-defined absolutethreshold.
 15. The apparatus of claim 12, in which the at least oneprocessor is further configured: to send the intra-RAT measurementreport when the signal quality of the current serving cell becomes lowerthan the first UE-defined absolute threshold and the signal quality ofan intra-RAT neighbor cell becomes higher than the second UE-definedabsolute threshold.
 16. The apparatus of claim 12, in which the at leastone processor is further configured: to send the inter-RAT measurementreport when both the UE and the network support the inter-RAT handoverwhile in the current status of the call setup, and the signal quality ofeach of the current serving cell and an intra-RAT neighbor cell becomelower than the first UE-defined absolute threshold.
 17. The apparatus ofclaim 12, in which the at least one processor is further configured: todelay sending the intra-RAT measurement report when a signal qualitydifference between the current serving cell and an intra-RAT neighborcell is below a UE-defined relative threshold; and to send the intra-RATmeasurement report when the signal quality difference between thecurrent serving cell and intra-RAT neighbor cell is above a relativethreshold.
 18. The apparatus of claim 11, in which the at least oneprocessor is further configured: to delay sending the inter-RATmeasurement report when a current call is in the call setup or when atleast one of the UE, the serving network or the target network do notsupport the inter-RAT handover during the call setup.
 19. The apparatusof claim 11, in which the at least one processor is further configured:to reduce a frequency of inter-RAT measurements when at least one of theUE, the serving network and the target network does not support theinter-RAT handover while in the current status of the call setup. 20.The apparatus of claim 11, in which the current status of the call setupcomprises one of: alerting, pre-alerting, before default bearerestablishment for signaling, after default bearer establishment forsignaling, before dedicated bearer establishment for traffic, and afterdedicated bearer establishment for traffic.
 21. A method of wirelesscommunication at a network, comprising: determining whether to delaysending to a user equipment (UE) an inter-radio access technology (RAT)handover command or an intra-RAT handover command based at least in parton a current status of a call setup and whether the UE and a networksupport an inter-RAT handover while in the current status of the callsetup, the network being a serving network or a target network; delayingsending the intra-RAT handover command for an intra-RAT handover holdingtime period and/or the inter-RAT handover command for an inter-RAThandover holding time period based at least in part on thedetermination; and sending the intra-RAT handover command and/or theinter-RAT handover command when the intra-RAT handover holding timeperiod and/or the inter-RAT handover holding time period expire, and/orthe call setup changes to the new current status in which both the UEand the network support the inter-RAT handover.
 22. The method of claim21, further comprising: adjusting the inter-RAT handover holding timeperiod and/or the intra-RAT handover holding time period based at leastin part on one of a UE speed measured at the network, a current servingcell radio frequency variation trend reported by the UE, a number ofintra and/or inter-frequency neighbors, application QoS specifications,a percentage of call setup completion, a signal quality of a servingcell and the signal quality of a target cell reported by the UE.
 23. Themethod of claim 22, further comprising: sending the intra-RAT handovercommand when the signal quality of the serving cell reported from the UEbecomes lower than a first network-defined absolute threshold and thesignal quality of an intra-RAT neighbor cell reported from the UEbecomes higher than a second network-defined absolute threshold.
 24. Themethod of claim 23, further comprising: sending the inter-RAT handovercommand to the UE when both the UE and the network support the inter-RAThandover while in the current status of the call setup, and the signalquality of each of the current serving cell and the intra-RAT neighborcell becomes lower than the first network-defined absolute threshold.25. The method of claim 21, further comprising: delaying sending theintra-RAT handover command when a signal quality difference between asignal quality of a serving cell and the signal quality of the intra-RATneighbor cell is below a first network-defined relative threshold; andsending the intra-RAT handover command when the signal qualitydifference is above a second network-defined relative threshold.
 26. Themethod of claim 21, further comprising: delaying sending the inter-RAThandover command when at least one of the UE, the serving network andthe target network does not support the inter-RAT handover while in thecurrent status of the call setup.
 27. An apparatus for wirelesscommunication, comprising: a memory; and at least one processor coupledto the memory, the at least one processor being configured: to determinewhether to delay sending to a user equipment (UE) an inter-radio accesstechnology (RAT) handover command or an intra-RAT handover command basedat least in part on a current status of a call setup and whether the UEand a network support an inter-RAT handover while in the current statusof the call setup, a network being a serving network or a targetnetwork; to delay sending the intra-RAT handover command for anintra-RAT handover holding time period and/or the inter-RAT handovercommand for an inter-RAT handover holding time period based at least inpart on the determination; and to send the intra-RAT handover commandand/or the inter-RAT handover command when the intra-RAT handoverholding time period and/or the inter-RAT handover holding time periodexpire, and/or the call setup changes to the new current status in whichboth the UE and the network support the inter-RAT handover.
 28. Theapparatus of claim 27, in which the at least one processor is furtherconfigured: to adjust the inter-RAT handover holding time period and/orthe intra-RAT handover holding time period based at least in part on oneof a UE speed measured at the network, a current serving cell radiofrequency variation trend reported by the UE, a number of intra and/orinter-frequency neighbors, application QoS specifications, a percentageof call setup completion, a signal quality of a serving cell and thesignal quality of a target cell reported by the UE.
 29. The apparatus ofclaim 28, in which the at least one processor is further configured: tosend the intra-RAT handover command when the signal quality of theserving cell reported from the UE becomes lower than a firstnetwork-defined absolute threshold and the signal quality of anintra-RAT neighbor cell reported from the UE becomes higher than asecond network-defined absolute threshold.
 30. The apparatus of claim29, in which the at least one processor is further configured: to sendthe inter-RAT handover command to the UE when both the UE and thenetwork support the inter-RAT handover while in the current status ofthe call setup, and the signal quality of each of the current servingcell and the intra-RAT neighbor cell becomes lower than the firstnetwork-defined absolute threshold.